This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-241523, filed Aug. 9, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fluid compressor of helical-blade type that constitutes, for example, the refrigeration cycle of an air conditioner.
2. Description of the Related Art
Reciprocating compressors and rotary compressors are known as compressors for use in, for example, refrigeration cycles of air conditioners. These compressors may become debased in sealing property or may be complicated in structure.
Recently, it is proposed that helical-blade type compressors be used in place of reciprocating compressors or rotary compressors. This is because helical-blade type compressors are relatively simple in structure, has improved sealing property and can compress fluid with high efficiency. In addition, the components of a helical-blade type compressor are easy to manufacture and assemble.
FIG. 11 shows a part of a helical type compressor. In this helical-blade type compressor, the roller 102 is eccentrically arranged in the fixed cylinder 101 and has a helical groove 103 in its outer circumferential surface. A blade 104 is fitted in the groove 103 such that it can move in the depth direction of the groove 104.
As the roller 102 revolves, the blade 104 divides the space between the cylinder 101 and the roller 102 into a plurality of compression chambers 105. Each compression chamber has a smaller volume than the immediately adjacent chamber that is more close to one end of the roller 102. The coolant gas introduced into the compression chamber 105 at that end of the roller 102 is gradually compressed to a high pressure until it is forced out of the compression chamber 105 provided at the other end of the roller 102.
As FIG. 12 shows, the helical groove 103 and the blade 104 have a rectangular cross section, taken along a line extending at right angles to their axes. Having a rectangular cross section, the helical groove 103 is easy to cut in the outer circumferential surface of the roller 102.
The blade 104 has a width a little smaller than the width of the helical groove 103. In other words, the widths of the groove 103 and blade 104 are predetermined so that the blade 104 can move in the depth direction of the helical groove 103.
Since the helical groove 103 and the blade 104 have a rectangular cross section, the blade 103 remains in contact with both sides of the helical groove 103 even when it completely lies within the helical groove 103.
Hence, the bottom space 106 defined between the lower surface of the blade 104 and the bottom of the helical groove 103 cannot sufficiently communicate with the high-pressure compression chamber 105A.
Consequently, the pressure of the coolant gas in the bottom space 106, which lies at the bottom of the helical groove 103, is lower than the pressure in the high-pressure compression chamber 105A. The coolant gas is inevitably forced out at a low pressure. Thus, the coolant gas cannot gain an optimal pressure rise. This may result in a decrease of compression efficiency.
When the blade 104 protrudes from the helical groove 103 to a maximum degree, it receives the highest possible pressure. At this time, the blade 104 is most deformed and cannot smoothly move with respect to the helical groove 103. This may degrade the sealing property of the compressor.
In the process of assembling the compression mechanism unit, the blade 104 having a rectangular cross section must be fitted into the helical groove 103 having a rectangular cross section. This work is extremely cumbersome, lowering the efficiency of assembling the compression mechanism unit.
An object of the present invention is to provide a fluid compressor in which the bottom space lying at the bottom of the helical groove can easily communicate with the high-pressure compression chamber to enhance the compression efficiency, and the blade can smoothly move with respect to the helical groove to improve the sealing property.
A fluid compressor according to the present invention comprises:
a hollow cylinder;
a roller provided in the cylinder, with an axis deviated from the axis of the cylinder, and having a helical groove made in an outer circumferential surface and having turns arranged at a pitch that gradually increases from one end to the other end;
a blade fitted in the helical groove of the roller and being movable with respect to the helical groove; and
a plurality of compression chambers provided between the cylinder and the roller, defined by the blade and designed to compress the fluid to a high pressure gradually as the fluid flows in an axial direction of the roller, from one end to the other end of the roller,
wherein the helical groove has one side positioned at a high-pressure compression chamber and another side positioned at a low-pressure compression chamber, and the one side and the another side are inclined at the same angle such that the groove gradually opens toward the outer circumferential surface of the roller, an opening angle xcex8 defined by the one side and another side is:
0xc2x0 less than xcex8xe2x89xa620xc2x0, 
the blade has one side positioned at a high-pressure compression chamber and another side positioned at a low-pressure compression chamber, and both sides of the blade are inclined at substantially the same angle as both sides of the helical groove.xe2x80x9d
The helical groove has one side positioned at a high-pressure compression chamber and another side positioned at a low-pressure compression chamber, and the one side is inclined to the another side such that the groove gradually opens toward the outer circumferential surface of the roller.
Thus, a gap develops between one side of the helical groove and one side of the blade, which opposes the side of the groove, when the blade moves, protruding from the helical groove. The space lying at the bottom of the helical groove therefore reliably communicates with the high-pressure compression chamber.